Bitumen based mixture for coating surfaces

ABSTRACT

A bituminous mixture, comprising from 0.5 to 20% by weight mineral wool in admixture with bitumen, the fibers of said mineral wool prior to any chemical or mechanical treatment, being equal to at most 7 per 5 grams, and said fibers being treated with a non-ionic finish.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a technique for coating surfaces withbitumen based mixtures, particularly for road surfaces and in particularmixtures for coating gravel.

2. Description of the Background

The bitumens used for surface coating to render them water-tight as inthe case of terraces or on surfaces on which vehicles run, i.e.,particularly roadways, when it is necessary to provide a road surfacewith a water impermeable layer by using a pervious bitumen bound stone,are almost never used in the pure state. Indeed, their high and lowtemperature performance is inadequate and, by themselves, they providesurfaces which are fragile, which break down under frost conditions andwhich, in contrast, become soft when exposed to heat. In order toimprove the behavior of the bitumens and above all the coating materialsand in order thus to widen the range of temperatures in which they canbe used, various substances are added to the bitumen, from the mostbanal such as crushed powdered lime, to the most sophisticated such asstyrene-butadiene-styrene based macromolecules. Inter alia, a well-knownalternative is to add various quantities of fibrous materials such asasbestos, rock fibers or glass fibers to bitumen. These additives widenthe range of temperatures over which the bituminous mixtures may beused. However, the use of such mixtures for the production of drainagecoatings in which one seeks to limit crushing under load at hightemperature remains inadequate, i.e., only uses under low loading and/orat limited temperature are possible. Under a heavy loading or underconsiderable heat, the bitumen flows and the interstices between thegravel become obstructed, and then drainage is no longer feasiblethrough the surfacing of the roadway.

Specific disclosures of the incorporation of mineral fibers intobitumen, include for example, Swedish Patent Se 211 163, which disclosesthe use of a filler, in bitumen, which is mineral fibers having a meandiameter of between 5 and 10 μm with lengths of between 0.1 and 5 mm. Bycontrast, more recently, European Patents EP 55 233 and EP 58 290 havedisclosed the use of fibers having a mean diameter of 1 to 5 μm, whichare treated with a cationic wetting agent under particular mixingconditions.

A need continues to exist for a bitumen based mixture of improvedproperties for coating surfaces.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide abituminous mixture which may be combined with gravel for use as aself-draining surfacing material under any circumstances.

Another object of the invention is to widen upwardly the temperaturerange in which the bituminous mixture may be used such that themechanical behavior at elevated temperature of the bitumen is improved.

Briefly, these objects and other objects of the present invention ashereinafter will become more readily apparent can be attained by abituminous mixture comprising from 0.5 to 20% by weight mineral wool inadmixture with bitumen and having a micronaire before any chemical ormechanical treatment of at least 7 per 5 grams, the fibers having beentreated with a non-ionic finish.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1 is a diagrammatic view of a machine which prepares the fibrousnodules of the present invention;

FIG. 2 is a DANIEL gauge;

FIG. 3 shows comparative results of tests on the DANIEL gauge; and

FIG. 4 shows results obtained from the ball and ring test.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An aspect of the invention is a method of producing a bitumen basedmixture with mineral wool in which a mineral wool is first produced andthen the virgin fibers are treated with the finish described above.Thereafter, the fibers are dried and nodules are formed by passing thefibers through a sheet with holes of an average size between 3 and 30mm. Finally, the mineral fibers are mixed with the bitumen.

In an alternative method, the mean size of the holes in the plate isbetween 6 and 15 mm and is preferably 10 mm in the case of a micronaireof 6 per 5 grams or 8 mm in the case of a micronaire of 4 per 5 grams.

The invention likewise provides for a method of manufacturing a mixtureof gravel for producing highway surfaces, compact or self-draining. Themethod also applies to the production of mixtures intended for thewaterproof surfacing of roofs or walls such as of a dam.

Inter alia, the technique of the invention makes it possible to producebituminous mixtures which are entirely suited to the technique ofdraining coatings. In particular, the stability under temperature ismarkedly better. It is thus that the so-called "ball and ring" test isimproved by a value which may be as much as 18° C. Similarly, thepouring test on the DANIEL gauge is improved by 40%.

Thus, the invention makes it possible substantially to improve theperformance of bituminous mixtures containing a given proportion offibers or, if the conditions of use allow it, it is possible to retainthe performance levels achieved with conventional fibers but with a farsmaller proportion of fibers, for example 3% instead of 5%, whichrepresents a considerable saving of fiber.

For the production of fibers which are to be added to bitumen, fibersare first produced. Fibers of desired diameter and length can beprepared from a molten material such as a blast furnace slag or a glasscomposition, and then optionally sizing the fibers with an organiccompound in solution. The fibers can then be dried and thenpolymerization occurs. The fibrous mat is adapted to the function ofbeing an adjuvant to bitumen and then is finally packaged. At the momentthe fibers are combined with the bitumen, they have a length of lessthan 500 μm.

The chemical composition of the mineral fibers, like their method ofmanufacture, does not in itself play any determining role in theiradaptation to the function of bitumen adjuvant. For example, the methoddescribed in EP patent 59 512 for the production of rock fibers and thatof EP patent 59 512 for the production of glass fibers makes it possibleto achieve the desired result. The only factors which have been shown tobe important are the fineness and length of the fibers produced.

The specialists in the production of mineral fibers are well aware ofthe difficulties which have to be met in industrial production in termsof diameter and length of the fibers. Obviously, it is possible to takesamples from the mat under production and to observe under a microscopethe fibers which are collected. It is possible to note the diameter andlength of each of the fibers observed in the optical field and it ispossible to calculate the arithmetical means. Thus, a mean diameter anda mean length are ascertained. If numerous measurements of this type arecarried out and if one assumes that the taking of samples is notdestructive, particularly in terms of length, then one can obtainfigures which are representative of the fiber mat. But these two factorsof diameter and length are not independent. The more drawn out fiberswill be the thinner fibers and the length and diameter will thereforeseem a priori to be parameters which vary in opposite directions, but onthe other hand, the thinnest fibers are also the most fragile and theymay break during the first phases of production and are likely to becomeshorter than the coarsest fibers. It happens that an important parameterfor the reinforcement of a bitumen is the specific surface area of thefiber elements introduced into the bitumen. The diameter does not takeinto account the specific surface area and therefore it does notcorrectly define the capacity of a given batch of fibers to be used as areinforcement for the bitumen.

During the course of tests to perfect high performance reinforcedbitumens, it has been found that there is one magnitude which couldserve to judge the capacity of a fiber mat for fulfilling the role of abitumen reinforcement: the micronaire. Measurement of the micronaire,also referred to as the "fineness index", takes into account specificsurface area by measuring the loss of aerodynamic head when a givenquantity of fibers extracted from a mat which is not lubricated issubject to a given pressure of a gas--generally air or nitrogen. Thismeasurement is conventional in mineral fiber production units; it isstandard (DIN 53941 or ASTM D 1448) and it uses a so-called "micronaire"appliance. The tests according to the invention are conducted with aSheffield machine type FAM 60 P. This machine comprises an intake forair or nitrogen under pressure, a valve for regulating this pressure, aflow meter, a cylindrical chamber of vertical axis with inlets for gasesat the bottom. The fibers weighed (more often than not 5 g±0.01 g) arepressed into the bottom of the chamber by a calibrated stopper whichallows the gases to escape. A preliminary test makes it possible toadjust the rate of flow of air to a given value always the same prior tocommencing the fiber buffer test. Measurement of the micronaire of thefineness index consists in recording the reading given by the standardflow meter when the fiber is in place. To work within the same range oflosses of head, it is necessary to adapt the quantity of fibers testedby reducing the mass when the diameter diminishes. It is thereforenecessary to mention this latter feature of reduced mass at the sametime as the result of the rate of flow. The tests according to theinvention have shown that a condition required in order to obtain a highperformance bitumen is a micronaire of less than 7 for 5 grams.

This factor, the micronaire, makes it possible to monitor the extent towhich a given batch of fibers is or is not suitable for bitumenreinforcement.

At the time of production of rock fibers or glass fibers, it isconventional to spray onto the fibers a liquid which makes it possibleto coat them with a so-called size and which, according to its nature,makes it possible to adapt the fibers to the use for which they areintended.

With regard to reinforcement of the bitumens, in the prior art nothingis placed on the mineral fibers as a size (SE 211 163) or a cationicwetting agent (EP 55 233 or EP 58 290) is added to the fibers.

Certain other techniques envisage using, in order to coat gravel, withor without the addition of mineral fibers, bitumens to which are addedadjuvants which are intended to favor engagement of the bitumen on theother elements of the final mixture. These adjuvants are either cationicwetting agents (DE-AS-17 19 350) or they are amines (US-4 166 752 orFR-2 181 882). All of these lubricants or these adjuvants are thereforeionic compounds.

Within the framework of the invention, on the other hand, an aqueoussolution of a non-ionic wetting agent is sprayed onto the rock fibers oronto the glass fibers intended for reinforcing the bitumen, just aftertheir processing. Excellent results have been obtained with solutions ofamine oxides such as dimethyl alkyl amine oxides and, in particular, thecases where the alkyl radical is a fatty acid radical. A preferred amineoxide is dimethyl stearyl amine oxide.

Once the fiber mat has been obtained with a good micronaire and with asuitable sizing, the step which remains is to make the fibers compatiblewith the conditions of use of the bitumen. This conditioning comprisesthe production of nodules and the way they are packaged.

Nodules are usually produced in two stages. In the first stage, thefiber mats are converted to flakes or flock which are/is converted tonodules in a second stage.

To produce the flock, a shredder is used which essentially comprises twoparallel cylinders rotating in opposite directions and having fingerswhich, between the cylinders, intersect with each other without touchingone another. At the outlet from the shredder, a pneumatic conveyor picksup the flock and carries it to a second apparatus which is shown inFIG. 1. This is a "nodulizer". It comprises an inlet pipe 1 and anoutlet pipe 2. The upstream space 3 is separated from the downstreamspace 4 by a wall 5 of metal plate in which there are holes. The platehas the form of a cylinder which is coaxial with a rotary drum 6carrying cutters 7 of which the cutting edge 8 is slightly inclinedrelative to their common axis. Facing the movable cutters 7 are fixedcutters 20 whose distance relative to the mobile cutters is adjustable.A distance of the order of a few millimeters, in particular 2 mm, isappropriate. The holes have a diameter of between 3 and 30 mm,preferably 6 to 15 mm according to the origin of the fibers and theirmicronaire. At the outlet from the nodulizer, the tube 2 is connected toa second pneumatic transport circuit by a slide valve which allowspassage of the nodules without disturbing the air circuits. The finaloperation carried out at the mineral fiber production site is thepreparation of the nodules which are either delivered into containers inbulk or they are packaged in bags of plastics film. In this case,polypropylene is preferably chosen.

The production of a coated gravel product according to the invention iscarried out as follows and this is presented by way of example. First ofall, 1600 kg of a mixture of calibrated gravel and filler (powder) arecombined in a container. Prior to such introduction, the gravel ispreheated to 160° C. Immediately thereafter, the fibrous nodules areintroduced according to the invention (8 kg) into the mixture withoutremoving them from the polypropylene bag. The liquid bitumen of type60/70 (82 kg) is likewise at a temperature of 160° C. and is introducedinto the container in turn. After being mixed for 2 minutes, thepreparation is ready to be used for surfacing a roadway. By depositing 4cm on an impermeable substrate, a layer of draining coating is obtained,the porosity of which is approx. 20% and it has a greater capacity forwithstanding heat than do the conventional coating materials.

To test the qualities of a bitumen mixture intended for coating gravel,several methods can be used. FIG. 2 diagrammatically shows the "DANIELgauge". This apparatus comprises two elements which are at right-anglesto each other, a chute 9 and a plate 10. The DANIEL test is carried outin two stages. In the first stage the chute 9 is horizontal and theplate 10 is vertical. The chute is filled with the hot mixture to betested, the top surface is levelled and the mixture is allowed tostabilize at 40° C. for 16 hours. After this period, the chute is tiltedvertically and one can see how the mixture spreads over the horizontalplate. This is engraved with parallel lines 11 which are equidistantlyspaced at 3.175 mm. After 4 hours in an environment of 40° C., theposition on the plate of the edge of bitumen which is most remote fromthe base of the chute is recorded. The number of gaps separating thisedge from the base constitutes the result of the DANlEL gauge test. Thehigher the figure the less satisfactory will be the behavior of theproduct when it is exposed to temperature.

Another currently used test is the ball and ring test. This test isstandardized (NF-T 66008, DIN 195 U4 or ASTM D 36-76). The principle isvery simple. A steel ball of specific mass is placed on a sample of theproduct contained in a ring of metal and of standard dimensions. Thewhole assembly is heated with a constant rise in temperature of 5° C.per minute. The temperature at which the sample becomes fairly soft, sothat the ball penetrates the bituminous product and becomes encasedtherein to a specific thickness, is taken as the softening point of theproduct being investigated. Thus, the test result is given in the formof a temperature and the higher the temperature the better is thebehavior of the product when exposed to heat. It must however be pointedout that values in excess of 75° C. are given solely by way ofindication and their relative position becomes uncertain in this zone.

Results of the DANIEL gauge test are shown in FIG. 3. On the abscissaone can achieve the percentage by weight of fibers which constitute theonly adjuvant introduced into the bitumen while the ordinates show theextent of flow obtained on the plate. The general trend is that thegreater the quantity of a fiber of a given type, the less it flows inthe mixture. Of the three curves 12, 13 and 14, Curves 12 and 13correspond to a fiber with a micronaire which is respectively 6 and 4,in both cases for 5 grams, this fiber having been sized with aquaternary amine in an aqueous solution (Lubromine NP).

On the other hand, curve 14 corresponds to a fiber having the samemicronaire before sizing as that in curve 12 although its coatingresults from being treated by means of an aqueous solution of dimethylstearyl amine oxide. It will be observed that the improvement providedby the treatment with this tension-active non-ionic agent depends on thequantity of fibers. It makes it possible to obtain an improvementamounting to several tens of percent.

FIG. 4 shows results of the ball and ring test. The abscissa representsthe percentage by weight of mineral fiber fillers in the pure bitumen.The ordinates show the temperature of the mixture at which the ballpasses through the bitumen. Graphs 15 and 16 correspond to a micronaireof 6 per 5 grams, while curves 16 and 18 have a value of 4, still withrespect to 5 grams. All these curves for each percentage show valueswhich are the arithmetical means of several experimental results. Here,the improvements are even more spectacular because at a concentration of5% they achieve 6° C. for micronaire 6 and 17° C. for micronaire 4. Asin the case of the DANIEL test, it can also be seen here that thetreatment carried out on the fiber allows a micronaire of 6 to enjoy abetter performance than a micronaire of 4.

The preceding tests were carried out with a nodulizer provided with agrid having openings 6 mm in diameter. Other tests were carried out at aconstant micronaire (4 for 5 grams) with a stearyl dimethyl amineoxide-based size by varying the diameters of the circular holes in thegrid. They are varied from 2 to 10 mm. In each case 5% of fibers wasfirst mixed in a beaker with 2 liters of bitumen 50-70 at 150° C. byusing a Raineri turbine. The operation is continued for 5 minutes. Atthe end of this time, the homogeneity of the mixture is observed usingthe eye, in the majority of cases it appears satisfactory. It is onlyfor the diameter 10 mm that it was necessary to repeat the agitation fora second period of 5 minutes before obtaining a mixture having ahomogeneous appearance. When mixing is completed, the ball-ringtemperature measurement test is carried out. Concurrently, nodules ofdiffering diameters, the same as those which have been used to make themixtures tested for ball and ring temperature, have been observed withthe scanning electron microscope. The length of all the fibers visiblein the field of view was then measured and the average of these lengthswas calculated, and also the proportion of fibers which have a lengthgreater than 0.5 mm. The results are shown in the table:

    ______________________________________                                        nodules     fibers          Ball-and-                                         (φ openings)                                                                         length               ring temp.                                    mm         μm     % 0-0.5 mm (°C.)                                  ______________________________________                                        2          --        --         57                                            4          105       96         61                                            6          255       85         65                                            8          330       78         78                                            10         490       65         81                                            ______________________________________                                    

Checks on the bitumen mixed under the preceding conditions have shownthat the length of the fibers is only slightly modified by the "gentle"mixing operation carried out here.

It is apparent from the preceding test that the method of preparation ofthe nodules proposed by the invention permits the length of the fibersto be controlled and protects them until they are introduced into thebitumen. It also shows the influence of this same length on thetemperature behavior of the mixture, and the limit on the choice ofgreater lengths (larger nodules) resulting from mixing difficulties.

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

In the following examples, tests are presented which were carried outwith micronaires (or mean diameters) which differed with sizes--ionic ornon-ionic--which vary in different quantities and with modified nodulesand varying proportions of fibers.

EXAMPLE 1

The fiber was a glass fiber centrifuged with a micronaire of 4 per 5grams. The lubricating solution consisted of Lubromine NP dissolved inan equal quantity of water. The quantities sprayed on were such that theamount of size was 0.42% by weight in relation to the fiber. Drying wascarried out while the fiber were being transferred to the conveyor belt.

The resultant fiber mat was then cut up and transported to the shredderdownstream of which was the nodulizer equipped with a grid with holes 8mm in diameter. The nodules were then collected at the outlet and mixedwith bitumen in a proportion of 5% by weight.

The "ball and ring" test was then conducted and a temperature of 69.0°C. was found.

EXAMPLE 2

The conditions were the same as for Example 1, except that the lubricantconsisted of a dimethyl stearyl amine oxide. This product was diluted at50% in water and made it possible to obtain sizing at the rate of 0.48%of the weight of fibers. Introduced at the rate of 5% into a 60/70bitumen, the fibers, prepared as nodules as in Example 1, make itpossible to attain a temperature of 75.3° C. in the ball and ring test.

EXAMPLE 3

In this example, the conditions are exactly the same, including thenature of the size, as in Example 1. The difference is in theconcentration of the Lubromine NP which here is 1 part to 2.30 partswater by volume producing a size percentage of 0.17% which produces aball and ring temperature of 66.8° C.

EXAMPLE 4

This test is likewise conducted with the same fibers, the samemicronaire, the same "nodulizing" technique (same diameter of holes inthe grid) as previously. The same sizing as described in Example 2 wasused which is dimethyl stearyl amine oxide diluted in water in aproportion of 1 part to 1.4 parts water. The sizing obtained is then0.28% by weight. It makes it possible to attain a ball and ringtemperature of 78.8° C.

EXAMPLES 5 AND 6

Examples 5 and 6 employ a thicker centrifuged glass fiber with amicronaire of 6 per 5 grams. In Example 5, the lubricant is Lubromine NPwith a concentration in the water of the original liquid of 30% byvolume and the resultant size level is 0.25% in relation to the weightof fibers. Thus, a ball and ring temperature of 59.6° C. is achieved. InExample 6, on the other hand, the size is based on the same amine oxideused previously; it is diluted in exactly the same way which supplies alubricant proportion of 0.20%. Here the result was 63.0° C.

EXAMPLE 7

Example 7 uses the same fiber prepared in the same way as Example 6except with regard to preparation of the nodules. Here, they areproduced with a sheet metal plate in which there are holes (5, FIG. 1),the diameter of which is 10 mm. The result obtained is better than withthe plate with the 6 mm holes since the temperature is 66.5° C.

EXAMPLE 8

This is identical to Example 7 except with regard to the nature andconcentration of size. Here, a fatty amine oxide was also used but thefatty acid radical was that of laurylic acid. A 30% solution in waterwas then made up to obtain sizing at the rate of 0.17% by weight, whichproduced roughly the same result as before: 66.1° C.

EXAMPLE 9

Examples 9 and 10 use a fine fiber with a micronaire of 4 per 5 grams.The nodules are made with a sheet metal plate with 8 mm holes, but thequantity of fibers introduced into the bitumen in this case is 7.5% byweight. In Example 9, the size was dimethyl stearyl amine oxide dilutedat 30% in water to provide sizing at the rate of 0.15% over the weightof fibers. Under these conditions, the result achieved was 77.1° C. forthe ball and ring test.

EXAMPLE 10

All the conditions of preparation were identical to those in Example 9except for the use of dimethyl lauryl amine oxide instead of dimethylstearyl amine oxide. It is diluted at the rate of 30% in water providinga quantity of size of 0.14%. It use resulted in a ball and ringtemperature of 80.3° C.

The foregoing examples show that the technique of the present invention,by offering a method of preparing mineral fibers intended forreinforcing a mixture of gravel in bitumen is different from the priorart techniques, both in terms of the initial quality of the fibers,i.e., fineness and length, and in terms of the nature of the lubricantsand the use of nodules which, prepared under clearly defined conditions,make it possible to produce coatings, the properties of which aremarkedly improved in relation to those of other techniques. This makesit possible either to retain the same performance, while reducing thequantity of fibers to be added to the mixture, or to enjoy a substantialimprovement in performance for one and the same cost.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. A method of producing a bituminous mixturecontaining mineral wool, comprising:preparing mineral wool at amicronaire of at most equal to 7 per 5 grams of mineral wool; treatingthe virgin fibers with a non-ionic finish which has an amine oxide baseand drying the treated fibers; passing a flock of said finished virginfibers thorough a plate having holes from 3 to 30 mm average size,thereby forming mineral wool nodules; and mixing said mineral wool fibernodules and bitumen to form said bituminous mixture.
 2. The methodaccording to claim 1, wherein said flock is formed by shredding saidfinished fibers between two parallel cylinders rotating in oppositedirections.
 3. A method of producing a bituminous mixture containingmineral wool, comprising;preparing mineral wool at a micronaire of atmost equal to 7 per 5 grams of mineral wool; treating the virgin fiberswith a non-ionic finish which has a base of an oxide of adimethylalkylamine and drying the treated fibers; passing a flock ofsaid finishied virgin fibers through a plate having holes from 3 to 30mm average size, thereby forming mineral wool nodules; and mixing saidmineral wool fiber nodules and bitumen to form said bituminous mixture.